1. Field of the Invention
The present invention relates to a Schottky barrier diode.
2. Description of Related Art
A Schottky barrier diode includes a semiconductor layer and a Schottky metal in contact with the semiconductor layer. A Schottky barrier is formed at an interface of the semiconductor layer and the Schottky metal. A plurality of structural examples of Schottky barrier diodes are disclosed a Japanese Patent No. 3691736. The structural examples to be compared with the invention of the present application are as follows. A first structural example (FIG. 11A of the Japanese Patent No. 3691736) is called a planar type and a Schottky metal is formed on a flat top surface of a semiconductor layer. A second structural example (FIG. 11C of the Japanese Patent No. 3691736) is called a trench diffusion type and columnar impurity diffusion layers are formed at intervals inside a semiconductor layer and a Schottky metal is formed on a top surface of the semiconductor layer. A Schottky junction is formed between the semiconductor layer top surface and the Schottky metal outside regions of the impurity diffusion layers (outside trenches). A third structural example (FIG. 2 of the Japanese Patent No. 3691736) is called a trench MOS type and an oxide film is formed on inner walls of trenches formed at intervals in a top layer portion of the semiconductor layer and polysilicon is embedded inside the trenches so as to contact the oxide film. A Schottky metal is formed to contact the polysilicon and the semiconductor layer outside the trenches. A Schottky junction is an interface of the semiconductor layer top surface and the Schottky metal outside the trenches.